The women's carnage continues at the Brisbane International with world number three Garbine Muguruza the latest big name to succumb to injury.

Muguruza was unable to overcome a left foot problem and retired hurt early in the second set of her second-round clash with American Varvara Lepchenko, losing 7-6(11/9), 1-0 on Wednesday night at Pat Rafter Arena.

The 22-year-old Spaniard, one of several up-and-comers tipped to challenge the dominance of Serena Williams this year, was granted a medical timeout between sets and bravely attempted to play on but was unable to do so, throwing her Australian Open preparations into disarray and the Brisbane event into further chaos.

Muguruza said she started to feel the injury in her heel at 3-3 in the first set and initially suspected new orthotics might be the cause.

But the Venezuelan-born right-hander said the problem traces back to last season and the condition, known as plantar fasciitis, only flared up since returning to the court in preseason.

"I'm not really worried because I felt it a lot, so it's really necessary to do a lot of treatment and to keep it (from) getting worse," she said.

"I will see now with my team and find out the problem and try to solve it as quick as possible.

"Hopefully it's gone in couple of days."

Muguruza is not entered into next week's Sydney International and said she will wait and see how her foot recovers before plotting her next move, but said the Open was her first priority.

Her injury follows the pre-tournament withdrawals of drawcards Maria Sharapova and Simona Halep and comes on the same day Williams pulled out of the Hopman Cup in Perth, also due to injury.

Indeed, of the current WTA top 10, only two players have played and won a match this week - Poland's Agnieszka Radwanska and Germany's Angelique Kerber.

"It's been a weird week for sure. A lot of players have been with some problems," Muguruza said.

Kerber is now the top seed in Brisbane and the highest-ranked player left in the field.

Kerber advanced to the semi-finals after beating Anastasia Pavlyuchenova 6-4, 6-4 on Thursday.

Lepchenko moves onto a quarter-final match-up against Spain's Carla Suarez Navarro, who took down injured Australian hope Samantha Stosur, and impressed in the relatively short time she was on the court.

"I thought she was playing good. For sure she has been practising," Muguruza said of Lepchenko.

"I think it's always sometimes hard to play the first matches, but (she was) really solid and motivated to play."